The conventional method of recovery of grease and oils from waste streams such as kitchen waste streams is that of using manual labor to-scrape and carry solids, oils, fats and greases from the cooking area to a container where the material is removed by others for direct rendering. Where fryers are used in large quantities, such as the cooking of French fried potatoes, the fryer oil is filtered and cleaned daily and the removed material is manually carried to a recovery tank for pick-up or collection. In the best of operations, a certain amount of solids, oils, fats, and greases contaminate the waste water stream.
Since municipal sewage treatment plants are not equipped to process these contaminants, all restaurants and the like are required to install a grease trap. This is reasonably effective if the residue is removed on a regular basis by pumping. Some establishments also utilize special organisms, which are put into the grease trap to break down the oils, and greases and minimize the impact of any escape of oils, fats, and greases from the grease trap to the downstream plant. Many cities and towns are beginning to recognize the detrimental impact of virtually any oil and grease into the treatment plant and are requiring more extensive removal of fats and oils or they are levying stiff fines for excessive amounts of these contaminates. The primary effect of these fats and oils is reduced capacity of the treatment plant and excessive cleaning of the waste water treatment plant which results in excessive cost and treatment time to process the entire waste water stream.
It has long been recognized that the plants and systems now in use are inadequate to properly remove solids, oils, fats, and greases from waste water streams. Employees of these plants must be properly supervised to minimize the inclusion of solids, oils, fats, and greases in the waste stream in an area where such supervision may be necessary for other more important operations and, consequently, there is less supervision of the former. Grease traps and oil removal traps must be pumped and maintained on a regular basis to operate properly and such proper maintenance is usually rare since the definition of xe2x80x9cregularxe2x80x9d is difficult to define.
In the prior art, various attempts have been made to address the problems set forth above. Examples of the known prior art patents are U.S. Pat. No. 4,113,617 U.S. Pat. No. 5,133,8871 U.S. Pat. No. 5,178,754 U.S. Pat. No. 5,225,085 and U.S. Pat. No. 5,504,538. These patents all show methods and or apparatus for the removal of oils and greases from kitchen waste streams but they involve the use of large fixed tanks. They are energy inefficient in that they require the addition of heat to melt or keep the oil or grease in a liquid phase.
In contrast to the prior art, the present invention can be mounted on a frame or a skid. It will have the approximate dimensions of 8 feet long by 4 feet wide and 6 feet high and thus it will take up a floor space of only about 32 square feet. Due to the above economy in floor space and the weight of about 700 pounds, the invention can be easily transported by a fork lift truck to the restaurant for installation. In the event major repairs are needed, the unit can be easily replaced with a new unit. A further advantage of the present invention is that the heat values of the kitchen waste stream are retained by the use of a Rankine cycle heat recovery system and thus, there is a saving in the energy bill for the user.
The invention comprises a process and apparatus for the recovery of oils from kitchen waste streams that contain water, oils, and food solids. The steps in the process are (a) removal of coarse food solids from said waste streams in a filtration zone, (b) separtion of the oils from the water in a separation zone at a temperature range and for a time period sufficient to produce a layer of oils and a layer of water, (c) removal of said layer of oils from the separation zone to a oil storage zone, (d) removal of water from said separation zone to a heat recovery zone, (e) transfer of heat values from said recovery zone to said separation zone with vapor compression refrigeration.